This invention relates generally to fuel supply and distribution systems, and, more particularly, to a hydraulic fuel flow distribution system for a gas turbine engine that can operate accurately in contaminated or gumming fuel situations.
In a gas turbine engine, fuel is generally supplied to a combustor or afterburner by a plurality of fuel injectors which receive a regulated flow of fuel from an interconnecting manifold. Between the manifold and each fuel injector, there is generally provided a plurality of relief valves having the same flow versus pressure drop characteristics. These relief valves are supplied fuel by the common manifold and supply fuel to flow tubes (vaporizing system), spray nozzles (atomizing systems), or spray bars (afterburners). A typical system may have twenty or more relief valves arranged in parallel. Each relief valve has a precise metering window which cooperates with a spring actuated metering piston to accurately schedule fuel flow for a particular pressure drop.
These valves are highly dirt sensitive in that they have pistons with sliding diametral fits of 0.0005 inches or less which cannot be protected by a reasonably sized filter. Consequently, relief valve, nozzle or spray bar replacement is a common field complaint because the internal valve is sticky. In addition, recent military specifications state that all fuel system components must pass the "qualification engine components test" which includes a contaminated fuel test. In the past, nozzles and spray bars have not been subjected to this test because they were considered part of the combustor or afterburner and not part of the fuel system.
U.S. Pat. No. 4,036,246 entitled "Fuel Supply and Distribution" by the inventor of the instant application sets forth a mechanical fuel and distribution system which overcomes many of the problems encountered in the past. However, this mechanical system still relies heavily, for proper operation, on many moving parts within the system. It therefore would be beneficial to provide a less complex hydraulic system capable of providing a fuel supply to a gas turbine engine or the like.